Make Action Massready to use in GI

Hello!

I’d like to know how i can make a specific Action mass ready to use/select in Generic Inquiries. 
I tried creating a action with the Customization Editor and using the following code to make it avaiable for mass processing. 

 

namespace PX.Objects.PO
{
  public class POOrderEntry_Extension : PXGraphExtension<POOrderEntry>
  {
    #region Event Handlers
            public override void Initialize()
        {
            processPurchaseOrderJW.IsMass = true;
        }
    #endregion
  }
}

This doesn’t work and fails on validation with “The name ‘processPurchaseOrderJW’ does not exist in the current context.

The Action is a Workflow Action and is suppossed to set two user defined checkboxes to true.

Would be glad to receive some ideas!
Thank you​​​​​​​